In suburban Maryland, a teen-ager runs over his dog and later shoots himself. In the District of Columbia, a 28-year-old railroad porter slashes his mother with a broken bottle and is shot and killed by police as he threatens to kill her. On Christmas Day 1983 in Randallstown, Md., a 14-month-old boy is decapitated by his father.

The connection between these and many other violent tragedies is PCP, a cheap, potent liquid that is the drug of choice among a growing number of Washington area teen-agers and young adults.

The drug ravages the brain cells of its users, causing unpredictable violent behavior, memory loss and uncontrollable reactions. Because it is absorbed and accumulated in the body's fat cells, psychotic flashbacks can occur months, even years later.

Despite widespread knowledge of its destructive properties, smoking PCP-laced cigarettes has become an accepted part of life among many poor teen-agers in Washington, which is second only to Los Angeles in the nation in its number of PCP abusers. Several of the young men involved in the gang murder of Catherine Fuller, a mother of six from their Northeast neighborhood, described their days as an endless round of looking for money to buy PCP.

It is a cheap high for the user, but an expensive burden for society.

"We're seeing a generation of chronically mentally ill people being developed where the mental illness is totally preventable," said Dr. Gladys Baxley, director of the D.C. Mental Health Services Administration, who said PCP users are "glutting" the city's emergency mental health system. "The kids are burning their brains out on a drug."

PCP is overwhelming the police, mental health system, schools and hospitals that are attempting to cope with it. For example:

*Approximately 34 percent of juveniles facing charges in D.C. Superior Court who agreed to testing since March 1984 have PCP in their systems, according to the Pretrial Services Agency. The figure jumps to 55 percent for those 18 to 21 years old.

*Drug arrests for PCP possession or sale in the District have increased ten-fold in the last four years. In 1981, police made 310 arrests involving the drug. Because of increased drug activity and police attention, by last year the number of arrests had soared to 3,030.

*More than one-third of those admitted to the emergency unit of St. Elizabeths, the public mental hospital in Southeast Washington, are experiencing violent psychosis because of PCP. Seventy-five percent of emergency cases handled by the city's Crisis Resolution Unit, which is set up to aid the mentally ill, involve PCP users.

The need for special hospital care is so great that the city is negotiating a contract with D.C. General Hospital for a 20-bed unit solely for PCP abusers. The cost will be at least $3 million yearly.

*Hallucinations and lethargy experienced by at least a dozen children treated at Children's Hospital in the last two years have been traced to PCP toxins. Some of the victims are as young as 2 months. "Some are in comas, others are drooling, with slurred speech and passing out," said Joyce Thomas, director of the child protection unit. "PCP when smoked in the presence of young children can result in the loss of a life."

The hallucinogen is "epidemic in the Washington community and endemic in the young black community," said Conrad Hicks, a psychiatric social worker who directs the South Mental Health Center on the grounds of D.C. General Hospital. "It's the most dangerous drug I've witnessed."

Once a little-known drug, PCP has grown into a major local health problem because of its low cost and wide availability.

Thin tinfoil packets of PCP-laced marijuana or parsley sell for $10 on the street, a price that has remained constant over the years. The quantity is enough to roll three slender cigarettes.

"When youths smoke PCP, they have four hours of numbness, eight hours of mellow and three days of coming down," said Jimmy Hendricks, regional director of Second Genesis, a District drug treatment center. A psychiatric social worker added, "With your whole social situation of unemployment, this is a resource they're using to escape."

Theodore, a 24-year-old D.C. native being treated for PCP abuse, said friends at Cardozo High School introduced him to the drug. "When you are on PCP, you have the right things to say, slick stuff . . . . I am an only child, and I had not done a lot of exciting things in my life. I was afraid of people, afraid of bullies. By using PCP, I got a macho image."

After five arrests for possession and selling PCP, another District native, Paul, 24, decided to take the judge's offer for treatment instead of jail. "I hung out with older people," Paul said. "I see them using PCP and I followed the crowd. I figured it might hurt them but it wouldn't hurt me."

Because the synthetic drug is an easy combination of six chemicals, clandestine laboratories producing it have sprouted throughout suburban Maryland and Virginia and the District.

"We estimate that 50 percent of the PCP trade is suburbanites," said Inspector Kris Coligan, director of the D.C. police Morals Division.

Warren Carmichael, spokesman for the Fairfax County police, said, "We are seeing an increase in PCP sales and use in the county." The 121 arrests in 1984 involving the drug was double that of the previous year.

Local arrests for PCP manufacture and sale have netted government chemists, lawyers, even police officers.

The labs they operate are unsophisticated operations in apartment kitchens or out of 55-gallon drums in rural back yards. Explosions, often killing or severely injuring lab operators, are another frequent byproduct of labs because of the chemicals' flammability.

Police take credit for closing many of the local labs, but they are frustrated by plentiful imports from California and Florida.

U.S. Park Police say the drug is "extensively available" in local parks, particularly at Hains Point and Franklin Park. High C. Irwin, commander of the Park Police's narcotics unit, said arrests have increased more than six-fold since 1980, with 424 arrests involving PCP in federal parks in Washington last year.

Prevention efforts are dwarfed by the plentiful supplies. "It's like water through a sieve," said Baxley. "It's like we're taking one step forward and 12 steps back."

PCP, unlike other drugs, is not seen in every city. Only Los Angeles, Washington, New York, Chicago, Baltimore and a few other inner cities on the coasts have high rates of PCP abuse, according to federal records of emergency room admissions. "Cocaine is everywhere, but there are pockets of PCP use," said Ann Blanken, an epidemiologist with the National Institute on Drug Abuse.

In Los Angeles, psychologists say a Hispanic macho attitude encourages young males there to flirt with a drug of such devastation. District experts say unemployed black youths are attracted to the drug because it is cheap.

It is a drug so dangerous that police agents wear rubber suits for fear of touching it. It is a drug so powerful that drug dogs that accidentally inhale too much of it have to be retired.

Perverse incidents also are typical in some outbursts by PCP users. "Hideous mutilations are not uncommon with PCP," said Dr. J. Theodore Brown, chief psychologist at D.C. General Hospital. "The youths who pushed a long cylindrical object into their victim; that is highly correlated with PCP," he said, referring to the Fuller murder.

Investigators have not determined possible motives behind the decapitation of a 5-year-old Adelphi boy this month. The boy's aunt said that the child's mother, who has been charged with murder in his slaying, smoked PCP, a charge also made by the woman's former boyfriend. The mother's court-ordered psychiatrist said it is too early to determine if drug abuse was a factor.

National Institutes of Health researcher Dr. Thomas O'Donohue said that one PCP-crazed woman in a Washington hospital tore the skin off her face with her fingernails because she believed that she was covered with insects. In another case, he said, a man in Los Angeles tore out his own eyeballs.

"We treat it like it is radioactive, but on the street they are smoking it," said Special Agent Robert J. O'Leary of the U.S. Drug Enforcement Administration's 10-year-old PCP Task Force, which covers the Washington region.

There has been no lack of attempts by local institutions to deal with PCP. Prevention programs, counseling, police crackdowns and special task forces abound.

Last year, District lawmakers tried stiffer penalties, tripling the jail term for those who make, distribute or use the drug to 15 years, and doubling the fine, to $100,000. The mayor established a blue ribbon task force on the subject.

In Maryland, the legislature acted in 1979, doubling the maximum prison term and fine for PCP sale or manufacture to 10 years and $20,000. In Virginia, possession carries a one-to-10-year sentence and a $1,000 fine. Those charged with intent to distribute or manufacture face a five-to-40-year sentence and a $25,000 fine.

Since 1983, when the D.C. Board of Education required teachers and administrators to learn how to identify drugs and abusers, 3,500 of the 5,000 affected employes have completed the 30-hour course. A special unit on PCP was added last year to the curriculum of all junior and senior high schools.

Lonnie Mitchell, director of the city's Alcohol and Drug Abuse Services Administration, said the program will be doubled this year. "There isn't any lessening in its PCP availability or its use," he said, noting that the city is paying private firms to open two 25-bed drug treatment centers for adolescents this spring.

Local police officers say they are stymied in their efforts to protect themselves and others from those deranged by PCP. Police officials outlawed the choke hold after a highly publicized incident in which Darryl Rhones, 24, a suspect in a shooting and later found to have used PCP, died after a choke hold was used during officers' attempts to subdue him.

"We asked the city government to give each officer a Taser a stun gun if we couldn't use a choke hold," said Gary Hankins, an official of the D.C. Fraternal Order of Police. "We didn't get a Taser issued, and we lost on the limitations. So now an officer has only his gun to use to protect himself . . . . It is only a matter of time until someone does shoot a PCP user who is violent. Then there will be a hue and cry because we shot him."

The dispute on how to subdue users led to a $400,000 jury decision against the city in December 1984. The widow of a PCP user who was shot and paralyzed by a police officer successfully sued the city for failing to properly instruct its officers on how to handle drug-crazed people.

The widespread use of the drug has forced most local police units to offer special training on dealing with PCP users.

The misery caused by this drug is demonstrated in hundreds of local tragedies, as the drug has become a kind of liquid insanity defense for unimaginable crimes.

The fatal scalding and stabbing of a 4-month-old infant, James Megenhardt Jr., in Glen Burnie, Md., in April 1984 was one such case. A neighbor, who said he was high on PCP and believed that the child was filled with demons, was sentenced to 30 years in prison for the killing.

"I think of PCP as the armpit of drugs," said Detective Ray Brett, a D.C. narcotics squad expert. "It is dirty, explosive, poisonous."

PCP devastates its users as well as its innocent victims. It can take up to two years for the body to be rid of the drug. Sometimes clear thinking and unimpeded speech never return.

After six months of withdrawal, Paul, now a resident at the Second Genesis drug treatment center, related, "My speech is a lot better now. When I came here it took a couple of minutes to get a word out."

The consequent mental debilitation is compounded by respiratory problems, because the harsh chemical components in PCP irritate lungs. Some dealers, lacking the drug, wet marijuana or dried parsley with other perilous substances that duplicate the chemical odor of PCP.

"They are being embalmed alive," Hendricks, of Second Genesis, said of PCP users. "They get it sprayed with roach spray and formaldehyde. Sellers will use anything to give it the chemical aroma and make it wet."

Many drug experts are mystified why such a drug, whose effects are so devastating, remains so popular.

"There's been so much bad publicity, it's bizarre that anyone even uses it," said Blanken, of the National Institute on Drug Abuse. "In Haight-Ashbury in the '60s, people tried PCP and rejected it immediately. Everyone thought the drug had no future. And now, 20 years later, it's popular."

Users are reluctant to give up the drug. "Our theory is that people are getting out of jail and going right back to it," said Sgt. Ronald Ricucci, commander of Montgomery County's narcotics unit.

"Only a small percentage is willing to seek treatment," said Hicks, of the District's mental health center. "Some of the victims of this drug were people that once had a future."

Lt. Irwin, of the Park Police, blames the families and friends of youths involved with PCP.

"We went to a house where there was a mother, daughter, son and niece," he said last week. "The son had been selling PCP, and everybody approves. We find whole communities banding together to protect the people who sell it . . . . They will deny it or say, 'Who cares?' "

Hendricks, the Second Genesis director, likens the drug to an unrestrained creature devouring the city's young. "There is a monster in the community," he said, "and it's become our kids."